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nir/algebraic: Optimize ushr of pack_half, not ishr
authorIan Romanick <ian.d.romanick@intel.com>
Thu, 2 Apr 2020 19:14:12 +0000 (12:14 -0700)
committerIan Romanick <ian.d.romanick@intel.com>
Mon, 11 May 2020 19:07:01 +0000 (12:07 -0700)
When a = -1.0, pack_half_2x16(vec2(0x0000, 0xBC00)) will produce
0xBC000000.  The ishr will produce 0xFFFFBC00.  The replacement
pack_half_2x16(vec2(0xBC00, 0x0000)) will produce 0x0000BC00.

Fixes: 1f72857739b ("nir/algebraic: add some half packing optimizations")
Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Cc: Connor Abbott <cwabbott0@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4515>

src/compiler/nir/nir_opt_algebraic.py patch | blob | history

diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py
index f9ebd5af4adfd400126a2f4dd95de430ce97e35d..2122559e7d6a3fe9e8428b6eef986792ae515488 100644 (file)
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -1030,7 +1030,7 @@ optimizations.extend([
 
    # Optimize half packing
    (('ishl', ('pack_half_2x16', ('vec2', a, 0)), 16), ('pack_half_2x16', ('vec2', 0, a))),
-   (('ishr', ('pack_half_2x16', ('vec2', 0, a)), 16), ('pack_half_2x16', ('vec2', a, 0))),
+   (('ushr', ('pack_half_2x16', ('vec2', 0, a)), 16), ('pack_half_2x16', ('vec2', a, 0))),
 
    (('iadd', ('pack_half_2x16', ('vec2', a, 0)), ('pack_half_2x16', ('vec2', 0, b))),
     ('pack_half_2x16', ('vec2', a, b))),